// Creates new initialized session instance.
func newSession(stor storage.Storage, o *opt.Options) (s *session, err error) {
	if stor == nil {
		return nil, os.ErrInvalid
	}
	storLock, err := stor.Lock()
	if err != nil {
		return
	}
	s = &session{
		stor:       stor,
		storLock:   storLock,
		stCompPtrs: make([]iKey, o.GetNumLevel()),
	}
	s.setOptions(o)
	s.tops = newTableOps(s)
	s.setVersion(newVersion(s))
	s.log("[email protected] F·NumFile S·FileSize N·Entry C·BadEntry B·BadBlock Ke·KeyError D·DroppedEntry L·Level Q·SeqNum T·TimeElapsed")
	return
}

// NewWriter creates a new initialized table writer for the file.
//
// Table writer is not goroutine-safe.
func NewWriter(f io.Writer, o *opt.Options) *Writer {
	w := &Writer{
		writer:          f,
		cmp:             o.GetComparer(),
		filter:          o.GetFilter(),
		compression:     o.GetCompression(),
		blockSize:       o.GetBlockSize(),
		comparerScratch: make([]byte, 0),
	}
	// data block
	w.dataBlock.restartInterval = o.GetBlockRestartInterval()
	// The first 20-bytes are used for encoding block handle.
	w.dataBlock.scratch = w.scratch[20:]
	// index block
	w.indexBlock.restartInterval = 1
	w.indexBlock.scratch = w.scratch[20:]
	// filter block
	if w.filter != nil {
		w.filterBlock.generator = w.filter.NewGenerator()
		w.filterBlock.flush(0)
	}
	return w
}

func (s *session) setOptions(o *opt.Options) {
	no := dupOptions(o)
	// Alternative filters.
	if filters := o.GetAltFilters(); len(filters) > 0 {
		no.AltFilters = make([]filter.Filter, len(filters))
		for i, filter := range filters {
			no.AltFilters[i] = &iFilter{filter}
		}
	}
	// Comparer.
	s.icmp = &iComparer{o.GetComparer()}
	no.Comparer = s.icmp
	// Filter.
	if filter := o.GetFilter(); filter != nil {
		no.Filter = &iFilter{filter}
	}

	s.o = &cachedOptions{Options: no}
	s.o.cache()
}

// NewReader creates a new initialized table reader for the file.
// The fi, cache and bpool is optional and can be nil.
//
// The returned table reader instance is goroutine-safe.
func NewReader(f io.ReaderAt, size int64, fi *storage.FileInfo, cache *cache.CacheGetter, bpool *util.BufferPool, o *opt.Options) (*Reader, error) {
	if f == nil {
		return nil, errors.New("leveldb/table: nil file")
	}

	r := &Reader{
		fi:             fi,
		reader:         f,
		cache:          cache,
		bpool:          bpool,
		o:              o,
		cmp:            o.GetComparer(),
		verifyChecksum: o.GetStrict(opt.StrictBlockChecksum),
	}

	if size < footerLen {
		r.err = r.newErrCorrupted(0, size, "table", "too small")
		return r, nil
	}

	footerPos := size - footerLen
	var footer [footerLen]byte
	if _, err := r.reader.ReadAt(footer[:], footerPos); err != nil && err != io.EOF {
		return nil, err
	}
	if string(footer[footerLen-len(magic):footerLen]) != magic {
		r.err = r.newErrCorrupted(footerPos, footerLen, "table-footer", "bad magic number")
		return r, nil
	}

	var n int
	// Decode the metaindex block handle.
	r.metaBH, n = decodeBlockHandle(footer[:])
	if n == 0 {
		r.err = r.newErrCorrupted(footerPos, footerLen, "table-footer", "bad metaindex block handle")
		return r, nil
	}

	// Decode the index block handle.
	r.indexBH, n = decodeBlockHandle(footer[n:])
	if n == 0 {
		r.err = r.newErrCorrupted(footerPos, footerLen, "table-footer", "bad index block handle")
		return r, nil
	}

	// Read metaindex block.
	metaBlock, err := r.readBlock(r.metaBH, true)
	if err != nil {
		if errors.IsCorrupted(err) {
			r.err = err
			return r, nil
		} else {
			return nil, err
		}
	}

	// Set data end.
	r.dataEnd = int64(r.metaBH.offset)

	// Read metaindex.
	metaIter := r.newBlockIter(metaBlock, nil, nil, true)
	for metaIter.Next() {
		key := string(metaIter.Key())
		if !strings.HasPrefix(key, "filter.") {
			continue
		}
		fn := key[7:]
		if f0 := o.GetFilter(); f0 != nil && f0.Name() == fn {
			r.filter = f0
		} else {
			for _, f0 := range o.GetAltFilters() {
				if f0.Name() == fn {
					r.filter = f0
					break
				}
			}
		}
		if r.filter != nil {
			filterBH, n := decodeBlockHandle(metaIter.Value())
			if n == 0 {
				continue
			}
			r.filterBH = filterBH
			// Update data end.
			r.dataEnd = int64(filterBH.offset)
			break
		}
	}
	metaIter.Release()
	metaBlock.Release()

	// Cache index and filter block locally, since we don't have global cache.
	if cache == nil {
		r.indexBlock, err = r.readBlock(r.indexBH, true)
		if err != nil {
			if errors.IsCorrupted(err) {
//.........这里部分代码省略.........

func recoverTable(s *session, o *opt.Options) error {
	o = dupOptions(o)
	// Mask StrictReader, lets StrictRecovery doing its job.
	o.Strict &= ^opt.StrictReader

	// Get all tables and sort it by file number.
	tableFiles_, err := s.getFiles(storage.TypeTable)
	if err != nil {
		return err
	}
	tableFiles := files(tableFiles_)
	tableFiles.sort()

	var (
		maxSeq                                                            uint64
		recoveredKey, goodKey, corruptedKey, corruptedBlock, droppedTable int

		// We will drop corrupted table.
		strict = o.GetStrict(opt.StrictRecovery)

		rec   = &sessionRecord{}
		bpool = util.NewBufferPool(o.GetBlockSize() + 5)
	)
	buildTable := func(iter iterator.Iterator) (tmp storage.File, size int64, err error) {
		tmp = s.newTemp()
		writer, err := tmp.Create()
		if err != nil {
			return
		}
		defer func() {
			writer.Close()
			if err != nil {
				tmp.Remove()
				tmp = nil
			}
		}()

		// Copy entries.
		tw := table.NewWriter(writer, o)
		for iter.Next() {
			key := iter.Key()
			if validIkey(key) {
				err = tw.Append(key, iter.Value())
				if err != nil {
					return
				}
			}
		}
		err = iter.Error()
		if err != nil {
			return
		}
		err = tw.Close()
		if err != nil {
			return
		}
		err = writer.Sync()
		if err != nil {
			return
		}
		size = int64(tw.BytesLen())
		return
	}
	recoverTable := func(file storage.File) error {
		s.logf("[email protected] recovering @%d", file.Num())
		reader, err := file.Open()
		if err != nil {
			return err
		}
		var closed bool
		defer func() {
			if !closed {
				reader.Close()
			}
		}()

		// Get file size.
		size, err := reader.Seek(0, 2)
		if err != nil {
			return err
		}

		var (
			tSeq                                     uint64
			tgoodKey, tcorruptedKey, tcorruptedBlock int
			imin, imax                               []byte
		)
		tr, err := table.NewReader(reader, size, storage.NewFileInfo(file), nil, bpool, o)
		if err != nil {
			return err
		}
		iter := tr.NewIterator(nil, nil)
		if itererr, ok := iter.(iterator.ErrorCallbackSetter); ok {
			itererr.SetErrorCallback(func(err error) {
				if errors.IsCorrupted(err) {
					s.logf("[email protected] block corruption @%d %q", file.Num(), err)
					tcorruptedBlock++
				}
			})
		}
//.........这里部分代码省略.........